Effects of Replacing Corn with an Aged Brown Rice–Wheat Mixture on Laying Performance, Egg Quality and Nutrient Digestibility in Laying Ducks

This study examined the effects of replacing corn with an aged brown rice (ABR)–wheat mixture (ABR: wheat = 85%:15%) on laying performance, egg quality, yolk fatty acid profile, economic benefits, serum biochemistry, and nutrient digestibility in laying ducks. A 12-week trial with six hundred 32-week-old Jinding ducks were randomly divided into five groups, with 10 replicates per group, and each replicate contained 12 ducks. The levels of ABR–wheat mixture in the diet were 0%, 12.5%, 25%, 37.5%, and 50%, respectively, to replace equal amounts of corn. The basic diet of the control group was corn–soybean meal (corn accounted for 50%). The experimental period was 12 weeks (from 32 to 43 weeks old). No significant differences were observed in laying performances (<i>p</i> > 0.05). From a numerical perspective, the duck-housed laying rate and egg mass were highest in the 37.5% group and lowest in the 50% group. Yolk color declined linearly (<i>p</i> < 0.05) over 12 weeks. The albumen height and Haugh unit showed a quadratic increase in weeks 4 and 8 (<i>p</i> < 0.05). The relative content of monounsaturated fatty acids (MUFA) increased linearly (<i>p</i> < 0.05), while the relative content of polyunsaturated fatty acids (PUFA), ω-3 PUFA, ω-6 PUFA, and ω-6/ω-3 PUFA decreased linearly in egg yolks (<i>p</i> < 0.05). The triglycerides (TG) content in serum showed a significant secondary change (<i>p</i> < 0.05), with the 50% group significantly lower than the other treatment groups (<i>p</i> < 0.05). The apparent digestibility of ether extract (EE) in the diets decreased linearly (<i>p</i> < 0.05). The apparent digestibility of crude protein (CP) in the diets was significantly reduced with the 50% group (<i>p</i> < 0.05), while there was no significant difference between the 0% and 37.5% groups (<i>p</i> > 0.05). Compared with the control group, economic analysis revealed net gains of 0.04–0.10 USD/duck at ≤37.5% substitution, but a loss (−0.04 USD) at 50%. In conclusion, the ABR–wheat mixture could reduce the yolk color and yolk PUFA content, but it could improve albumen quality and increase yolk MUFA content. High-level ABR–wheat mixture (50%) significantly reduced the TG content in serum and nutrient digestibility of the diet and also showed a numerical decrease in laying rate and egg mass. Our findings suggest that up to a 37.5% ABR–wheat mixture can effectively replace corn in laying duck diets without negatively affecting laying performance, while improving albumen quality and altering yolk fatty acid composition.